<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>

<c:url var="actionUrl" value="/subs/subscribeForm" />
<form action="${actionUrl}" method="POST" >
    <c:set var="xz" value="${periodical.name}" scope="session" />
periodical: ${xz}<br>
month count: <input type="number" name="count" >
</form>